Buttercream

In a large mixing bowl, whip the eggs until light and fluffy.
In a small saucepan bring the sugar and the corn syrup to a boil. Lubricate the inside of a metal baster with a small amount of vegetable oil and dispense it completely. Then use this to drizzle the sugar mixture into the mixing bowl with the eggs. The mixer should be on low speed until you finish drizzling in all of the sugar mixture.
Once the entire mixture of the sugar is incorporated, slowly add the butter pieces. Only add more butter when you can no longer see the previously added pieces. It will go fast at first and then slow down. Continue to whip until the mixture is creamy.

*RAW EGG WARNING
Food Network Kitchens suggest caution in consuming raw and lightly-cooked eggs due to the slight risk of Salmonella or other food-borne illness. To reduce this risk, we recommend you use only fresh, properly-refrigerated, clean, grade A or AA eggs with intact shells, and avoid contact between the yolks or whites and the shell.